Method for forming a multipart plastic article



Sept- 9, 1952 E. L. DANlELsoN ET AL 2,609,570

METHOD FOR FORMING A MULTIPART PLASTIC ARTICLE Filed Jan. 22, 1951 4Sheets-Sheet 2 FLOYD J. Dor-SEN BY ATTORNEYS Sept. 9, 1952 E. DANlELsoNETAL 2,609,570

METHOD FoR FORMING A MULTIPART PLASTIC ARTICLE Filed Jan. 22, 1951 4sheets-sheet 4 3Q ab 39 /1 l /1 w37 3,7 E; j? :5v-v 37 a 37a :E W l gv'26 /Qgw /g!//// 26%- '25 25 27 *264. .1 l5- :XI '37a 37h ,3'7 y l A39`37 '26a 39 ////z\v//// 4 3a Ew-\ wm 27 "2.5 l Af. d farla- 35 EFL LJ.

37a. BY L .OYD OFS'EN Bi \\//////1\ www A raw 27 25 25a' l A TORNEYSPatented Sept. 9, 1952 OFFICES" METHOD FOR FORMING A MULTIPART i PLASTICARTICLE Elmer L. Danielson, Oakland, and Floyd J. Dofsen, San Francisco,Calif.

Application January 22, 1951, Serial No. 207,174

7 Claims. 1

The present invention relates to improvements in a method for forming amulti-part plastic article with mechanical interlocks. It embodiesmodifications and improvements over our copending application, SerialNo. 203,992, filed in the United States Patent Oiiice on January 2,1951, entitled: Method for Forming a Composite Plastic Structure.

In our copending case, as identified above, we cast a rst part of theplastic structure, with pro-- jections extending from a surface thereofagainst which a second plastic part is to be cast. Thereafter, thisprecast part is placed in a cavity provided in one die of a mold, andthen a second die is moved into coacting relation with the first toclose the mold. During the closing of the mold, the projections areautomatically deected,

or upset, and are retained in these positions by the dies. Uponinjecting the material for the second plastic part of the compositestructure, it is conveyed over the surface of the precast part andaround the deflected projections to embed the latter therein. Theseprojections mechanically interlock the two plastic parts.

Our present invention provides for precasting a first plastic part;inserting this part into a cavity of a first die; and then closing theopen end of the cavity with a second die. 'I'his follows the samegeneral pattern as in our copending application. However, the second dieto be disclosed in the instant case has at least one chisel thereon. Asthe two dies are closed, this chisel is disposed for cutting into anddeflecting a portion of the precast part. This portion is maintained inits deflected position during the casting of a second plastic partagainst the rst, with the deflected portion serving as a mechanicalinterlock between the two plastic parts. j

In certain species of the present invention, we provide preshapedprojections on the precast plastic part. Chisels of various shapes areutilized on the second die for cutting into and deflecting, orspreading, portions of the projections of the precast plastic part.These chisels hold the deflected or spread projections in position whilethe material for the second plastic part is cast therearound.

Other objects and advantages will appear as the specification continues.The invention consists of the steps of the method, as hereinafterdescribed and claimed.

DRAWINGS For a better understanding of our invention, reference shouldbe had to the accompanying drawings, forming part of this application,in which: l

Figure 1 is a rear plan view of a precast plastic part for an article,this part having projections extending from a surface thereof againstwhich a second plastic part is to be cast;

Figure 2 is a vertical sectional'viewA taken along -the plane II-II ofFigure l, portions being shown in elevation;

Figure 3 discloses this precast part (Figure 1) disposed in a mold diecavity, with a second die inserted into the rst die so as to close thecavity, the second die havingr 'wedge-,shaped'chisels splitting theprojections and deecting portion of each projection in oppositedirections;

tions on the precast plastic part being' spread at their tops byconical-shaped chisels ofgthe upper or second die; n y l Figure 7 is aview similar` to Figure 6, after the injection of the material for thesecond vplastic part has been accomplished; Figure 8 is an elevationalview, partly in section, of this second specie of Vour multi-partarticle; f

Figure 9 is a rear plan view of a modied form of precast first part, inwhich projections are provided along a flange of this part, ,whichy areadapted to be cut and deected to provide mechanical interlocks in thefinal article;

Figure 10 is a sectional YView partly in elevation, taken along the lineX-X of Figure v9;

Figure 11 illustrates this modified precast part as being disposed inthe cavity of aclosed mold, the upper die of which is provided withchisels for cutting and deecting the projections mentionedin connectionwith Figure 9;

Figure 12 is a View corresponding with Figure l1, but showing theinjection of the Plastic material for the second part injected into theclosed mold; y

Figure 13 is an elevational View, partlyin section, of the third specieof our multi-.part article; Figure 14 is a rear plan `view of a' further'specie of our precast rst part, in which diagonal fillets are providedat the corners of a marginal flange of this part;

Figure is a vertical sectional view taken along the inclined line XV-XVof Figure 14;

Figure 16 illustrates this precast part (Figure 14) as being disclosedin the closed dies of a modied mold;

Figure 17 is a sectional view corresponding with Figure 16, but showingthe injection of the second plastic material after it has beencompleted; and

Figure 18 is a vertical sectional view taken mechanical interlocksbetween the two plastic parts. A central core 22 is carried by the upperdie E to leave a recess 23 in the final article.

Second specie Our multi-part plastic article A2, and the modified lowerand upper dies D2 and E2, respectively, are shown in Figures 6 to 8,inclusive. When made initially, the precast first part B2, as used inFigures 6 8, is identical with that shown 4'in Figures 1 and 2.Accordingly, like reference through the fourth specie of our multi-partY plastic article. l Y,

While we have shown only the preferred forms of our invention, it shouldbe understood `that various changes, or modifications, may be madeWithin the scope of the appended claims without departing from thespirit thereof.

DETAILED DESCRIPTION First specie Referring now to Figures 1 to 5,inclusive, We have illustrated therein our method and mold for forming amulti-part plastic articlewhich is indicated generally at A. It includesa precast character. As shown herein, this characterconsists of theletter O.` The' projections i9 are formed integral with' and rise fromthe base.

For' the .purpose of completing the multi-part article A after theprecast part B has been made, We provide a mold that includes lower andupper dies D and E, respectively. The lowerdie has a cavity l5 therein,which is designed to receive and support the kprecast first part B (seeFigure 3),

`with the base Il resting on the bottom I'B of the .die cavity and theprojections upwardly.

kNow the upper mold E is brought into position to close the open end ofthe die cavity l 5. Corelike chisels I'I extendV .downwardly from thisdie and have wedge-shaped lower ends I8. These I 5 extending Vchiselsare axially alignedwith the projections.

As the mold is closed, the chisels cut into the projections Iii,deflecting lportions I ila of each projection in opposite directions.

It is 'quite apparent from Figure 3 that the deflected portions lila ofthe projections extend in angular-relation with and overhang the base Hof the precast rst part B. In otherv words, undercuts are providedunderneath the out- Wardly-.directed top .portions of the projections.

At this time, plastic material for the second part C of the finalarticle A is injected through an orifice I9 leading to the unoccupiedspace 15a of the die cavity. While the portions lila of the projectionsare held in oppositely-deilected positions by the lower ends ofthechisels, the incoming plastic ilovvs over the upper surface 2i) ofthe base I l and embeds the projections l0 therein.

Upon opening the mold, the completed article may be withdrawn, and theundesired sprue 2| removed. The parts B and C may be made of anyydesired contrasting colors. The split and deflected upper ends Yof theprojections provide numerals have been applied to corresponding parts.

Moreover, the lower die D2 in Figures 6 and 7 is identicalwith the lowerdie D previously described. Also, the upper die E2 is very similar tothe upper die E, excepting for the fact that it has conical-shaped lowerends 24 on its chisels lb. Again, we have used the same referencenumerals to designate corresponding parts of the molds in Figures 6-7and 1-5..

As 'clearly shown in Figure 6, the core-like chisels ill) are axiallyaligned with the projections t@ of the precast part B2. Accordingly,when the dies D2 and E2 are closed, the Aconicalshaped lower ends 24will penetrate into these projections, causing the upper portions IEi'b, of the latter to expand outwardly. Upon injectingthe plasticmaterial for the second `partCZ, as in Figure 7, this incoming materialwill ow over theupper surface 2B of the base Il, embedding theprojections therein and producing .mechanical 'int-erloclrs between theparts B12-C2.

Third specie Y Turning to the form of `our invention, as disclosed inFigures 9 to 13, inclusive, the third modied article A3 consists of aprecast first plastic part B3 Vanda subsequently-cast second part C3.

In its structural features, the part B3 is f-ashionedwith a base havinga marginal iiange 26 rising therefrom. This base is formed with a slot21 extending therethrough to receive material when the second part C3 iscast 4against the iirst. This will produce a character, which has beenillustrated as providing the letter O. Projections 28 are formed atintervals along the interior surface of the flange 2t.A As shown inFigure 9, one of these projections is disposed at the mid-point of eachend and side section 26a and 25h, respectively, of this marginal flange.Moreover, the projections extend downwardly and are formed integral withthe base 25.

vThe precast part B3 is placed in a cavity 29 provided in a lower dieD3, with its marginal an'gefiivfacing upwardly. Thereafter, an upper dieE3 is brought into the position shown in Figure 11 so as to form aclosure over this cavity.

"It will be noted that vchisels la'c project downwardly from the upperdie E3, and are provided withv wedge-shaped lower ends 39.l The latterare positioned to penetrate initially into the projections`2i3 along thedot-dash lines 3l (see Figure 9) As these chisels move downwardly,portions 28a of the projections Y28 are deflected toward the center ofthe precast part B3. j

Now the plastic material for the part AC3 is injected through an orifice32 so lasv to 'fill the vremainder of the cavity 2.9, as shown in Figure1.2. This incoming materialiiows over the upper surface 25a of the base25, and embeds the delected portions 23a therein. A central core 35, maybe provided on the die D3 for the purpose of leaving a recess 35 in thecompleted article A3 (see Figure 13). After this article is Withdrawnfrom the mold, the undesiredsprue36`y is removed. The deflected portionsZBmm'echanicallyjnter-'f lock the two parts B3 and 03.1,.;4 Y.

i i Fourth spec a,

{Referenee is Ymade to Figli 14 to 18, nclusive: The precast part B4S.,.C1u ite similalto `the part B3 just described. Like referencenumerals have been used to designatecorrespondingparts. However.diagonal fillets 31 are formed at the junctions of the end and sidesections 26a, and 2Gb, respectively, of the marginal flange 2'6 of thisprecast part (see Figure 14).

The lower die D4 is identical with the die D3, and has its cavity 29arranged to receive the precast part B4. Chisels Hd projectfdownwardlyfrom the upper die E4, and are fashioned with wedge-shaped lower ends38. The latter cut into the fillets 31 along the dot-dash lines 39 (seeFigure 14) as the chisels I'Id move downwardly, deflecting portions 31aof the llets 31 toward the center of the precast part (see Figure 16).

With the precast part B4 and the mold dies D4 and E4 arranged in themanner illustrated 'in Figure 16, plastic material for thesubsequentlycast part C4 is injected through the orifice 32 to ll theunoccupied space of the die cavity 29 (see Figure 1'1), producing thenal article A4. The incoming plastic material for the second part C4flows over the upper surface 25a of the base 25 and embeds the deflectedportions 31a, producing mechanical interlocks between the two parts inthe completed article A4.

1. In the herein describedmethod of forming a multi-part plasticarticle, which includes the steps of: precasting a plastic first part ofthe article with a surface against which a second part is to be cast;cutting into this precast part and bodily deflecting a portion thereoffrom a normal into an offset position overhanging said surface, with thedeflected portion and said surface defining an undercut; and thereafterinjecting plastic material for a second part of the article against saidsurface for flowing into the undercut and embedding the deflectedportion, while still maintaining said portion in its deilected positionuntil the second part solidies, whereby said portion will be precludedfrom returning to its original position and will mechanically interlockthe two parts.

2. The combination of steps as set forth in claim 1, in which thedeecting of a portion of the rst part into offset position isaccomplished simultaneously with the cutting into the precast part.

3. In the herein method of forming a multipart plastic article, whichincludes the steps of: precasting a plastic rst part ofthe article withat least one projection extending from a surface against which a secondpart is to be cast; cutting into this projection and bodily deflecting aportion thereof from a normal into an offset position overhanging saidsurface, with the deflected portion and said surface dening an undercut;and thereafter injecting plastic material for a second part of thearticle against said surface for flowarticlwith afsurface` againstfwhicha second part is to be cast; cuttingv into spaced-apart sectionsofjthisprecastpart and bodily deflecting portions of these-sectionstoward each other; these portions being deflectedfromnormal into offsetpositions overhanging said surface and de'- flning undercuts; andthereafter injectingplasticmaterial for a second part of .the articleagainst said surface for flowing into the undercuts and embedding thedeflected portions, while still maintaining said portions in theirdeflected positions until the second part solidifies, wherebyV timebodily spreading portions thereof in opposite directions from normalinto offset positions overhanging said surface; these vportions and saidsurface defining undercuts; and thereafter injecting plastic materialfor a second part of the article against said surface for flowing intothe undercuts and embedding the offset portions,

while still maintaining said portions in offset positions .until thesecond part solidies, whereby said portions will be precluded fromreturning to their normal positions and will mechanically interlock thetwo parts.

6. In the herein method of forming a multipart plastic article, whichincludes the steps of precasting a plastic first part of the articlewith at least one projection extending from a surface ing into theundercut and embedding the deflect- Tri against which a second part isto be cast; cutting into this projection and bodily deflecting a portionthereof from a normal into an offset position overhanging said surface,with the deflected portion and said surface dening an undercut; andthereafter injecting plastic material for a second part of the articleagainst said surface for flowing into the undercut and embedding thedeflected portion, while still maintaining said portion in its deflectedposition until the second part solidies., whereby said portion will beprecluded from returning to its original position and will mechanicallyinterlock the two parts; the deflecting of a portion of the projectioninto offset position being accomplished simultaneously with the cuttingthereinto.

7. In the herein describedmethod of forming a multi-part plasticarticle, which includes the steps of precasting a flrst part of thearticle with a surface against which a second part of the article istobe cast; placing this precast part in a cavity of a first die so as tobe supported by the wall of the cavity; moving a second die intocoacting relation with the flrst die to close the second part solidies,whereby said portion will y be precluded from returning to its originalposi- 7 8 tion and will mechanically nterlockrthe two -K QNITED STATESPATENTS Y parts- Number-1f?- j V 'Name Date ELMER L DANELSQN- 701,492Matthes June 3, 1902 FLOYD J- D0FSEN 5 1,200,992 `seams oct. 10, 191s A1,284,553 Apple` A Nov. 12, 1918 REFERENCES CITED 1,068,590 Hilfreich2.. May 8, 192s The following references are of record in the 2,062,880Hansen Dec. 1, 1936 le of =this`patent: 1 y 2,222,755 Watson Nov. 26,1940 2,483,832 Kingston Oct. 4, 1949

